1. Field of the Invention
The present invention relates to a data distribution system, distribution equipment, terminal equipment and a data distribution method, suitable for use in a data service system or the like for distribution of digital data, for example.
2. Description of Related Art
Recently, the video and audio data compression technology, and the digital signal processing technology in broadcasting and communication systems have shown remarkable innovations. In these situations, it has been proposed to organize between a user and server a data distribution system incorporating such advanced data compression technology and signal processing technology. Generally, the data distribution system is called “video on demand (VOD)” or “music on demand (MOD)” system and destined to distribute a digital data to a user getting access to the system. Such data distribution systems include a MOD system for data communication via an Internet system and a packet transmission system, for example.
In such a MOD system, however, the transfer rate is limited and a transmission being done is likely to be interrupted by any other one, which makes it difficult to transmit a digital data fluently with no congestion of the communication network over which the transmissions are made. When a music data, for example, is transferred over a data communications network from a server to a user in the conventional MOD system, the transfer rate of the communications network is very approximate, in many cases, to a data transfer rate required for reproduction of the audio data. In such a case, since the transfer rates are so approximate to each other that a continuity of the audio data cannot be assured downloading it into a hard disc or the like at the user's side (such a reproduction will be referred to as “real-time reproduction” hereinafter). Actually, there exists a problem that an audio data cannot be reproduced before the downloading is complete.
Further to the above, there is a case that a communications network, over which the MOD system transmits an audio data from a server to a user, has a maximum transfer rate of 28.8 kbps and a mean transfer rate of 22 kbps while the data transfer rate necessary for a real-time reproduction of the audio data is 32 kbps. In this case, since the data transfer rate required for real-time reproduction exceeds the transfer rate of the communications network, the received data cannot be real-time reproduced at the user's side.